A power spring is frequently used as a drive source for a musical box or toys. A winding key which is used to charge the power spring is generally connected, as by threadable engagement, with a winding shaft to which one end of the power spring is secured. This allows the key to be disengaged by turning it in the opposite direction. When such a winding mechanism is used in a toy used by an infant, a risk is possible that the infant may carry the key into his mouth as it is disengaged from the spring shaft. If the key is not put into the mouth, the key itself has a number of protuberances, which make it dangerous that the key be disengaged. To prevent this, the present applicant has previously proposed a winding key clamp which prevents the winding key from being disengaged once it is threadably engaged with a winding shaft (see Japanese Utility Model Publication No. 11,516/1976).
However, with the disclosed winding key clamp, when the winding key is turned in the direction opposite from the winding direction, a rotating drive is transmitted to a driven member contained within a toy through the winding shaft, thereby applying undue stresses upon the toy and to damage it.